1. Field of the Invention
This invention lies in the field of the smokeless burning of waste gases by means of flares.
Still more particularly, this invention relates to the construction of flares for the burning of very large flows of waste gas, of size 200,000 pounds per hour or greater.
Still more particularly, it concerns an improved type of construction for flares to burn large quantities of gas smokelessly with reduced expenditure of energy for pressurization of the primary combustion air.
2. Description of the Prior Art
In the prior art large high-powered flares for the smokeless burning of waste gas have been built, up to the size of about 100,000 pounds per hour, using the power of pressurized air for smokeless combustion. Such prior art devices were constructed in such a form that the primary combustion air was pre-pressured and pre-mixed with the waste gas in such a way that the total flow was in the form of a solid vertical cylinder of rapid upflowing gas and air, such that there was a large induction of secondary air around the outer periphery of this column of flame and gas.
Because of the surface area limitation to the flow of induced secondary air into the outer wall of the rising column of gas, and the necessity for the secondary air to penetrate to the center of the column in order to avoid incomplete and smoky combustion, there was a practical limit of the order of 100,000 pounds per hour for such flares. Such applications that had larger flows than this would require a duplication of two or more such flares to handle a total flow capacity.
By the present invention it is now possible to provide combustion of 200,000 pounds per hour in a single flare, or less with reduced expenditure of electrical energy for pressurizing the primary combustion air.
However, there is another serious problem in the smokeless combustion of hydrocarbons where the hydrogen to carbon ratio (H/C-R) is low. Ventings from an ethylene facility (principally olefinic, or unsaturated compounds) provides gases for smokeless flare burning where the H/C weight ratio can be as low as 0.166, and difficulty with smoky burning increases as the H/C ratio decreases. For example, consider methane (H/C=0.333) makes no smoke as it burns at the flare; ethane (H/C=0.25) makes faint trailing smoke, and propane (H/C=0.222) smokes relatively heavily. Smoke density increases as the H/C falls below 0.222, and difficulty in smoke suppression will vary as the potential smoke density increases. Thus, as the H/C-R decreases, means must be provided to increase the rate of induction of secondary air to provide smokeless combustion. With this invention it is possible to flare burn without smoke, large flows of waste gases, which are combustible, and which have H/C-R in the range of 0.333 down to 0.083 (acetylene).